Author Topic: BOSS DD-2 only output dry Signal  (Read 105 times)

tone5

BOSS DD-2 only output dry Signal
« on: July 12, 2018, 09:49:29 PM »
Hi,
my DD2 only output dry Signal,no problem with power(+9v and +5v),LED light,switch to Hold on function LED will turn light,
but no delay Signal form mono or stereo.

After trace signal IC7(main controller) pin31 signal in but no output from pin46

Any Idea where can go next? Thanks


Slowpoke101

Re: BOSS DD-2 only output dry Signal
« Reply #1 on: July 13, 2018, 06:18:53 PM »
Welcome to the forum and hopefully we can help with your problem.

Digital pedals can be a bit difficult to repair but I think that your DD-2 won't be too hard.
You found an audio signal going to pin 31 of IC7. Good. But the signal you found on pin 46 is not audio. It is data and will not sound anything like your initial audio input.
The delayed audio output from IC7 is found on pin 14 of the R73 resistor network. R73 is a R2R resistor network which converts the digital data from IC7 to an analog (audio) signal. If you use an audio probe you should be able to hear the delayed audio on pin 6 of IC6 assuming that IC7 is working. It is most likely fine and the problem will be elsewhere.

Old pedals can suffer from dried out electrolytic capacitors. The BOSS digital pedals are prone to this problem due to internal heat buildup. The pedal works for years and then suddenly stops working.
On the schematic, look at IC2 (NE570 compander) and the electrolytic capacitors connected to it (the symbol for these capacitors have a + symbol next to the capacitor). Using an audio probe check for audio on pin 7 of IC2 (this is audio going to IC7) - You probably have audio here anyway as you have some signal on pin 31 of IC7. Then check for delayed audio on pins 14 & 15 of IC2. Most likely you will not have delayed audio available. C39 and C34 are notorious for causing the problem that you have described.
Good luck and let us know what you find.
« Last Edit: July 13, 2018, 11:03:33 PM by Slowpoke101 »
..

ElectricDruid

Re: BOSS DD-2 only output dry Signal
« Reply #2 on: July 13, 2018, 07:12:07 PM »
+1 agree with Slowpoke.

Pin 46 is not audio. you'd be better checking for audio on pin 14 of R73 or on pin 6 pf the following 5534 op-amp.

No delayed audio could be caused by all sorts of things. Those 4066 switches might not be working, for instance. Or it could be something in the Compressor/Expander stages, as Slowpoke suggested. Or it could be a dead transistor in one of the output filters. Or a dead FET (Q8?) further along.

So long as the micro controller is working, none of them are super-difficult to fix. It's just a question of working through the circuit logically until you get to the point where the signal disappears.

HTH,
Tom



tone5

Re: BOSS DD-2 only output dry Signal
« Reply #3 on: Yesterday at 08:31:28 PM »
This is a very helpful information.
i will follow this step trace signal.Thank you

Welcome to the forum and hopefully we can help with your problem.

Digital pedals can be a bit difficult to repair but I think that your DD-2 won't be too hard.
You found an audio signal going to pin 31 of IC7. Good. But the signal you found on pin 46 is not audio. It is data and will not sound anything like your initial audio input.
The delayed audio output from IC7 is found on pin 14 of the R73 resistor network. R73 is a R2R resistor network which converts the digital data from IC7 to an analog (audio) signal. If you use an audio probe you should be able to hear the delayed audio on pin 6 of IC6 assuming that IC7 is working. It is most likely fine and the problem will be elsewhere.

Old pedals can suffer from dried out electrolytic capacitors. The BOSS digital pedals are prone to this problem due to internal heat buildup. The pedal works for years and then suddenly stops working.
On the schematic, look at IC2 (NE570 compander) and the electrolytic capacitors connected to it (the symbol for these capacitors have a + symbol next to the capacitor). Using an audio probe check for audio on pin 7 of IC2 (this is audio going to IC7) - You probably have audio here anyway as you have some signal on pin 31 of IC7. Then check for delayed audio on pins 14 & 15 of IC2. Most likely you will not have delayed audio available. C39 and C34 are notorious for causing the problem that you have described.
Good luck and let us know what you find.

tone5

Re: BOSS DD-2 only output dry Signal
« Reply #4 on: Yesterday at 08:41:03 PM »
Thanks so much,i will keep trace this week.

+1 agree with Slowpoke.

Pin 46 is not audio. you'd be better checking for audio on pin 14 of R73 or on pin 6 pf the following 5534 op-amp.

No delayed audio could be caused by all sorts of things. Those 4066 switches might not be working, for instance. Or it could be something in the Compressor/Expander stages, as Slowpoke suggested. Or it could be a dead transistor in one of the output filters. Or a dead FET (Q8?) further along.

So long as the micro controller is working, none of them are super-difficult to fix. It's just a question of working through the circuit logically until you get to the point where the signal disappears.

HTH,
Tom